The present invention relates to a head gimbal assembly of a disc drive, and more particularly, to a flexible interconnect circuit with improved damping properties for use in a head gimbal assembly.
Disc drives are well known in the art and comprise several discs, each disc having several concentric data tracks for storing data. A transducing head carried by a slider is used to read from or write to a data track on a disc. The slider is located on an actuator arm, and glides above the surface of the disc as the disc is spun. The slider is positioned above a data track on the disc by moving the actuator arm on which the slider is suspended using a large scale actuation motor, such as a voice coil motor.
The slider is mounted on the actuator arm using a head gimbal assembly (HGA). A standard HGA comprises a load beam, a gimbal, a flexible interconnect circuit, and the slider. The load beam provides the main support structure for the HGA. The gimbal is attached under the load beam, and the slider is attached to the gimbal. The gimbal is designed to allow the slider to follow the surface of the disc more closely than if the slider were mounted directly on the load beam. The flexible interconnect circuit is laid on top of the load beam and provides the circuitry to and from the head in the form of leads and traces. The leads and traces connect the flexible interconnect circuit to the slider and thus allow electronic signals to pass between the transducing head carried on the slider and the flexible interconnect circuit.
As the slider is moved by the actuator arm, the HGA experiences vibrations and reaches certain structural resonances. At structural resonances, the HGA begins to move wildly, which adversely affects the performance of the transducing head. Of particular concern is the first torsion resonance experienced by the HGA at a frequency of approximately 3,700 hertz.
Some structural resonances of the HGA""s are inevitable. Other resonance modes, in particularly the first torsion resonance, are controlled using damping methods. Past attempts at damping the structural resonance of the HGA, and in particular the first torsion resonance, involved adding a Mylar damper to the HGA. Mylar dampers have a self adhesive backing and are applied to the surface of the flex circuit. The adhesive on the damper acts to absorb the energy from the resonance, which results in reduced vibration of the HGA.
Due to the small size of the HGAs, applying the Mylar dampers creates complications and challenges during the manufacturing of the HGAs. In addition to requiring a separate piece part, additional assembly process steps are required, both of which increase the cost of the HGAs. Thus, there is a need in the art for a damping method which is simple to manufacture and inexpensive to incorporate into the assembly of HGAs.
The present invention relates to a damping method for damping the first torsion resonance in HGAs. By redesigning the flex circuit on the HGA to include an elbow or damping strips, it is possible to dampen the first torsion resonance without affecting the pre-load force on the load beam or making other resonance modes worse. This small design change in the flex circuit is inexpensive and can be incorporated into the manufacturing of the HGA without requiring a separate piece part or an additional assembly step.